Geomorphological Control Over Occurance of Arseniferous Aquifers in The

2nd International Symposia (2000)

The symposia on the Impacts of Toxic Chemicals and Pollutants on Public Health and the Environment was held on March 6-8, 2000 at Dhaka LGED Building Conference Room and in Calcutta Ram Krishna Mission, Goal Park, Ballyganj in March 9-11. In Dhaka, Dr. Derek Whitworth, Secretary General, IIBB and Prof. B. Choudhury, Kolkata University, served as symposia chairpersons in Dhaka and Kolkata, respectively

Abstracts of Paper

Geomorphological Control Over Occurence Of Arseniferous Aquifers in the Bengal Basin

A. B. Goswami, Retired Director, Geological Survey of India, presently Consulting Hydrogeologist and Water Resources Management Advisor

The Bengal Basin witnessed radical changes in the tectonic, geomorphic, hydrographic and hydrodynamic fronts during the Quaternary period. Variety of detrital sediments under different environments of deposition filled the basin as the sea receded to the present position. While a sequence of alluvial fan terraces occupied most of the northern part, another set of depositional terraces emerged in the shelf region of the basin between Late pleistocene and Late Holocene time. The eastern part of West Bengal in India and Bangladesh below the Ganga -Padma river is marked by the presence of Upper and Lower Deltaic sedimentsof Holocene age.

The coastal region displayed a series of dune ridges, interdunal flats, interdistributary marshes formed within 600 YBP indicating gradual recession of the sea. Incidentally, arsenic contaminated aquifers at shallow depth are restricted within the deltaic sediments constituting the Upper and Lower Delta plains. Older landforms and sediments are not affected yet. The occurrence and distribution of arseniferous aquifers indicate a linkage with the Quarternary, especially the Holocene geomorphology and sedimentation pattern.

This would provide an insight in searching for the source of Arsenic in ground water and in mitigating the problem. Key words: Geomorphological control, arseniferous aquifers, Bengal Basin.

Need For Integrated Study On Origin Of Arsenic In Groundwater In Bengal Basin

A. B. Goswami, Retired Director, Geological Survey of India, and former senior research scientist, School of Water Resources Engineering, Jadavpur University, presently Consulting Hydrogeologist and Water Resources Management Advisor and Tarak N. Mukherjee, Research Scholar

The Bengal Basin comprises the world's largest fluvio-deltaic complex built up by Ganga-Brahmaputra-Meghna river systems. It contains huge reserve of groundwater within the porous layers of the deltaic sediments of Late Holocene age.

High concentration, much beyond the permissible limit of 0.05 mg/l, of arsenic is found to contaminate the groundwater occurring in the deltaic sediments within 100 meters depth. The arsenic contamination in ground water has already emerged as severe bane in social and health fronts in eight districts of West Bengal in India and in forty one districts of Bangladesh covering the Upper and Lower Delta Plains of the Basin.

While the status of arsenic concentration in ground water in different parts of the affected area is known and supply of arsenic-free drinking water is being arranged in certain parts of the area, not much headway in identifying the source of arsenic could be noticed as yet except some uncoordinated, unauthenticated assumptions.

This calls for an integrated multidisciplinary approach with application of suitable modern technologists involving various knowledgeable scientists from different related fields of earth science to the in-depth study on the origin of arsenic in groundwater of the basin. (Key Words: Integrated study, origin of arsenic in groundwater, Bengal Basin)

Application of Activated Alumina-Based Arsenic Removal Units

Anirban Gupta, Pratip Bandyopadhyay, Ranjan K. Biswas, Swapan K. Roy and Morshed Alam Department of Civil Engineering, Bengal Engineering College (Deemed University) Howrah – 711 103, India

Vast areas of Bangladesh and West Bengal (India) are facing problem with high concentration of arsenic in their ground water that is used for drinking. Any long-term measure to supply safe surface water to the people in the arsenic-prone areas may be a capital-intensive venture, which will also need significant time to implement. The need, therefore, arises for suitable short-term (interim) measures for provision of safe drinking water sources. The arsenic-contaminated water from tubewells (hand-pumps) can be treated to make it fit for drinking. Among the candidate technologies for treatment, adsorption on activated alumina (AA) shows much promise. Based on our laboratory as well as field experiments, it was observed that (i) activated alumina can adsorb both As (V) as well as As (III), though the sorption of As (V) is more efficient, (ii) activated alumina can be suitably regenerated for reuse, once its capacity is exhausted, (iii) the treated water becomes more palatable as the iron content is also brought down, (iv) simple treatment units can be designed with AA for application in domestic as well as community-level, (v) the service life of the units in a single cycle is reasonable for practical application. The service life of domestic units was found to vary between eight months to two years in a single cycle, whereas the same for community-level units varies from eight months to eighteen months depending on the raw water arsenic concentration and also the daily intake through the Units. The AA bed in the domestic units is suitably housed in a specially designed bag for replacement during regeneration after it gets exhausted. For regeneration of the AA bed of the domestic units, it is suggested to be conducted in a central location and not in each household. However, the hand pump- attached units are designed in a way such that regeneration can be undertaken in situ. For regeneration, commercially available hydrochloric acid and caustic soda are needed and the local persons can be trained for this purpose. The spent regenerant contains high concentration of arsenic, and should not be disposed of in open drains or surface water bodies. A protocol has been developed to contain the arsenic in a limited volume of sludge, which can be subsequently subjected to cement-based stabilization. The occasional backwashing, which the hand-pump units should be subjected to for removal of the deposited iron flocs from the bed, would generate a backwash that contains higher concentration of arsenic. It has been found that more than 90% of the arsenic is associated with iron flocs and a sand bed is provided by the side of the Unit to arrest these flocs and the output through the bed contains low arsenic concentration. The sand in the bed along with the accumulated iron flocs (containing arsenic) may subsequently be subjected to similar cement-based stabilization. Such hand pump-attached units have been installed in ten places, which are working successfully. In four places of North 24 Parganas district (West Bengal), the beneficiaries formed a committee to take care of the operation and maintenance of these Units for which they are collecting a water tariff from the users. In Nadia district (West Bengal), a voluntary organisation is taking care of the Units. These units can also be dismantled and installed elsewhere, if alternative source of safe water is subsequently arranged by other means. It is felt that the activated alumina- based arsenic removal units may serve effectively to provide safe water to the people in the arsenic-prone areas, till any long-term and permanent measure can be implemented.

“Industries And Associated Toxins In The Bengal Basin”

Claudia J. Carr, Rishi Das, Rash B. Ghosh, Ya-Ting Liu and Hiro Nozaki

The Bengal Basin Working Group (BBWG) is a group of scientists, academics, students and concerned individuals, investigating the health crisis in the Bengal Basin. Our work has been inspired by recent contributions to the ongoing debate concerning the occurrence of toxins in the Bengal Basin - a debate that is clearly geared to involve members of the affected communities, professionals and officials. Regrettably, we were unable to attend the Congress due to unforeseen circumstances. However, we wish to contribute at least a portion of our information and perspective for your consideration and we look forward to future interaction and possible collaboration with members of the Congress. Many have contributed to the critical examination of the prevailing notion that the toxics crisis in the Basin is primarily attributable to naturally occurring arsenic. By now, substantial evidence has been produced that the crisis is not simply created by naturally occurring arsenic, and that the increased incidence of cancer, mortality, genetic defects and disease are derived from multiple toxins generated throughout the Basin. We have undertaken a preliminary identification of what some of these toxins might be and the industries they might be associated with. We have been approaching this problem partly through tracing these selected industries and the problems associated with them in many countries. Many of the toxins that we suggest might be contributing to the crisis in the Bengal Basin in fact pose similar health hazards in highly regulated economies. The industry/toxin correlations have been estimated conservatively, emphasizing only some known carcinogens and associated toxins. We have focused primarily on Bangladeshi portion of the Basin due to the far greater geographic and economic complexity of the Indian regions. The industries and toxics they produce have largely generated from economic development promoted throughout the Basin, the dangers of which are not readily apparent.

The following are some summary points from our work:

Massive amounts of groundwater pumping have been carried out for decades, particularly since the early 1970’s. The depths of this aquifer pumping have varied, but it is possible that arsenic and other toxins are coming up in ever-increasing amounts, with the accelerated pumping of aquifers, both for agricultural and industrial purposes. While it is proposed that shallow aquifer use be replaced by use of deeper ones in order to reduce the unintended extraction of these toxins, this does not address the source of the problem, nor does it provide a solution. As we shall note momentarily, the presence of toxins in groundwater systems is intricately related to a number of different industrial processes.

The extensive reliance on agricultural chemical inputs, namely, fertilizers and pesticides, raises questions about the direct toxicity of these chemicals, as well as their interaction with identified toxins in the Basin. As a case in point, phosphates are known to increase the leachability of arsenic and other toxins into the groundwater. Highly toxic pesticides, including organophosphates, carbamates and chlorinated hydrocarbons are known carcinogens, are widely used on paddy, jute and other crops, and may percolate into shallow aquifers. The extent to which these toxins, when released and circulated in the Basin, contribute to the current health crisis, remains unknown.

A preliminary investigation of some prominent industries in Bangladesh reveals a wide array of toxins that are likely contributors to the health crisis in the Basin. While these toxins may not have been measured in the Basin, they are known to be associated with these industries throughout the world. These toxins pose severe health hazards, even in developed countries, where strict regulatory and enforcement structures exist.

Cement manufacture commonly produces a whole host of solid and liquid toxic wastes, as well as toxic air emissions. The list includes the major carcinogens, dioxin and arsenic, and up to 15 heavy metals, including mercury, cadmium, lead and selenium. In the cement industry, hazardous wastes may be used as fuel, particularly in the lowest-income developing nations. This use of battery shells, used oil and benzene, contaminated soil and sludge and other wastes for fuel greatly increases the exposure of human populations to toxins.

The pulp and paper industries are chemical-intensive operations, which involve inputs and releases of highly toxic chemicals. At the worst end of the pollution spectrum, dioxins, arsenic, methyl iodide, formaldehyde, chloroform and nickel compounds are powerful carcinogenic products of the bleaching and dyeing processes. According to recent World Bank reports, fluorides, sulphuric acid, sulphur and nitrous oxides, and grease and oil may be directly dumped into rivers or released into the air. The World Bank says that downstream damages from such discharges include fish kills, paddy crop damage and poisoned drinking water. In numerous instances, affected communities responded with protests and violence. The most important of the toxins associated with this industry is dioxin. At least seven of dioxin’s chemical forms are highly toxic, and one of them is believed to be the single most carcinogenic compound in existence. Even in very low levels of exposure, dioxin causes birth defects and weakens the immune system, and disrupts the reproductive and endocrine systems. Other severe toxins, including fluoride and sulphur compounds, are found in wastewater and are commonly dumped into nearby waterways, or even in cases where they are removed by scrubbers, the liquid from scrubbers is itself discharged into the regional water supply.

Uranium mining and milling are developing within the Basin, with Indian and Bangladeshi operations increasing their activity. The World Bank has supported the Bangladeshi government’s plans for developing uranium extraction for export and energy generation (detail). Uranium deposits exist in the northeastern part of Bangladesh, the Khasi hills in Meghalaya, and also in the northwestern part of Bangladesh. Uranium mines like the Domiasiat uranium mine and mill in the Khasi hills produce enormous amounts of uranium tailings. Arsenic also occurs in the uranium ore, and is released, along with heavy metals like molybdenum and manganese in the tailings. The milling process uses acids and chemicals to dissolve the uranium, and about 90% of the radioactivity in the ore remains in the tailings.

The health impacts of uranium mining are catastrophic, and well documented. Radiation from uranium mines located in the state of Bihar have been linked to genetic mutation and slow death among the more than thirty tribes living in the southern Bihar. 30,000 people from 15 villages in the vicinity of the tailings pond suffered from skin lesions and disease, cancer, tuberculosis, fertility loss, bone and brain damage, kidney damage, hypertension, disorders of the central nervous system, congenital deformities, insomnia, nausea, dizziness, and pain in the joints and abdomen.

The focus by foreign investors and international aid on expansion of energy production in Bangladesh, particularly using natural gas, in recent years, will likely increase both the amount and the circulation of toxins within the basin. Increasing natural gas extraction can fundamentally alter aquifers and bring up water from deeper levels, and in the process, release arsenic and other toxins into water systems used for human consumption. Power production has its own toxic byproducts. Inadequate procedures for waste disposal, for example, lead to direct air discharges of sulphur and nitrogen oxides, and water discharges of copper from cooling systems, excess and unused fuels, lubricants, coolants and solvents. Power plants demand large amounts of water for cooling, which requires increased groundwater pumping - which can extract more arsenic from aquifers. Of equal or even greater significance is the fact that the power generated is primarily directed to industry use, which ultimately means increased toxic production.

Natural gas is a feedstock for the agrochemical industry, with gas liquids providing about 70% of the feedstocks for ethylene (ethylene is the most basic petrochemical produced; trichloroethylene is a known carcinogen). Moreover, natural gas comprises 85% of the inputs for urea fertilizer production - in which some processes use arsenic oxide for separation and produces extremely hazardous arsenic laden effluent. International aid agencies project that approximately $4 billion of investment in natural gas power generation over the next five years are “required”, and this matter should be of gravest concern for immediate investigation.

Urea fertilizer production, providing Bangladesh’s fifth largest export commodity, varies widely in its pollution intensity. There are some first order toxicity problems, however, which are generally associated with the industry, including the use of arsenic oxide and the production of arsenic discharge from at least one type of separation process, as just noted.

Another source of carcinogens and other major toxins is the leather, or tanning industry which constitutes a substantial percentage of Bangladesh’s economy. The chemicals released from leather processing are well documented and include cyanide based oils and dyes, chromium salts and formaldehyde - all of which are carcinogenic, and the wastes that may be discharged include lead, cyanide, and sulfides. These chemicals are potentially major contributors to the unfolding health crisis in the basin - a reality suggested by innumerable instances, such as chromium contamination of drinking water supplies by tanneries in Mexico.

In conclusion, it seems highly probable that the toxics crisis in the Bengal Basin is a broad based one involving many chemicals from multiple sources. We urgently call upon the Congress to support a thorough and swiftly executed program, to identify the specific sources of these toxins, their full manifestation in health and everyday life within the Basin, and potential solutions available. Such a program would surely involve those most affected throughout the Basin, as well as professionals and those in positions to expedite change. (End by reading quote, please)

“All people have a right to a clean environment. Material wealth, such as the guarantee of food, employment, subsistence, education, and health, will not make human life worthwhile without having clean air, water, and land… Recent incidences of ammonia contamination of rivers by the Ghorasal fertilizer factory, trace metal contamination of soils by the Hazaribagh tannery, arsenic contamination of millions of tube wells, and lead contamination of air will become catastrophic in proportion if no mitigation measures are taken.”

-Md. Khalequzzaman, Assistant Professor of Geology, Georgia Southwestern State University

“Industries And Associated Toxins In The Bengal Basin”

Prepared by Bengal Basin Working Group

The Bengal Basin Working Group (BBWG) is a group of scientists, academics, students and concerned individuals, investigating the health crisis in the Bengal Basin. Our work has been inspired by recent contributions to the ongoing debate concerning the occurrence of toxins in the Bengal Basin - a debate that is clearly geared to involve members of the affected communities, professionals and officials. Regrettably, we were unable to attend the Congress due to unforeseen circumstances. However, we wish to contribute at least a portion of our information and perspective for your consideration and we look forward to future interaction and possible collaboration with members of the Congress. Many have contributed to the critical examination of the prevailing notion that the toxics crisis in the Basin is primarily attributable to naturally occurring arsenic. By now, substantial evidence has been produced that the crisis is not simply created by naturally occurring arsenic, and that the increased incidence of cancer, mortality, genetic defects and disease are derived from multiple toxins generated throughout the Basin. We have undertaken a preliminary identification of what some of these toxins might be and the industries they might be associated with. We have been approaching this problem partly through tracing these selected industries and the problems associated with them in many countries. Many of the toxins that we suggest might be contributing to the crisis in the Bengal Basin in fact pose similar health hazards in highly regulated economies. The industry/toxin correlations have been estimated conservatively, emphasizing only some known carcinogens and associated toxins. We have focused primarily on Bangladeshi portion of the Basin due to the far greater geographic and economic complexity of the Indian regions. The industries and toxics they produce have largely generated from economic development promoted throughout the Basin, the dangers of which are not readily apparent. The following are some summary points from our work: Massive amounts of groundwater pumping have been carried out for decades, particularly since the early 1970’s. The depths of this aquifer pumping have varied, but it is possible that arsenic and other toxins are coming up in ever-increasing amounts, with the accelerated pumping of aquifers, both for agricultural and industrial purposes. While it is proposed that shallow aquifer use be replaced by use of deeper ones in order to reduce the unintended extraction of these toxins, this does not address the source of the problem, nor does it provide a solution. As we shall note momentarily, the presence of toxins in groundwater systems is intricately related to a number of different industrial processes. The extensive reliance on agricultural chemical inputs, namely, fertilizers and pesticides, raises questions about the direct toxicity of these chemicals, as well as their interaction with identified toxins in the Basin. As a case in point, phosphates are known to increase the leachability of arsenic and other toxins into the groundwater. Highly toxic pesticides, including organophosphates, carbamates and chlorinated hydrocarbons are known carcinogens, are widely used on paddy, jute and other crops, and may percolate into shallow aquifers. The extent to which these toxins, when released and circulated in the Basin, contribute to the current health crisis, remains unknown. A preliminary investigation of some prominent industries in Bangladesh reveals a wide array of toxins that are likely contributors to the health crisis in the Basin. While these toxins may not have been measured in the Basin, they are known to be associated with these industries throughout the world. These toxins pose severe health hazards, even in developed countries, where strict regulatory and enforcement structures exist. Cement manufacture commonly produces a whole host of solid and liquid toxic wastes, as well as toxic air emissions. The list includes the major carcinogens, dioxin and arsenic, and up to 15 heavy metals, including mercury, cadmium, lead and selenium. In the cement industry, hazardous wastes may be used as fuel, particularly in the lowest-income developing nations. This use of battery shells, used oil and benzene, contaminated soil and sludge and other wastes for fuel greatly increases the exposure of human populations to toxins. The pulp and paper industries are chemical-intensive operations, which involve inputs and releases of highly toxic chemicals. At the worst end of the pollution spectrum, dioxins, arsenic, methyl iodide, formaldehyde, chloroform and nickel compounds are powerful carcinogenic products of the bleaching and dyeing processes. According to recent World Bank reports, fluorides, sulphuric acid, sulphur and nitrous oxides, and grease and oil may be directly dumped into rivers or released into the air. The World Bank says that downstream damages from such discharges include fish kills, paddy crop damage and poisoned drinking water. In numerous instances, affected communities responded with protests and violence. The most important of the toxins associated with this industry is dioxin. At least seven of dioxin’s chemical forms are highly toxic, and one of them is believed to be the single most carcinogenic compound in existence. Even in very low levels of exposure, dioxin causes birth defects and weakens the immune system, and disrupts the reproductive and endocrine systems. Other severe toxins, including fluoride and sulphur compounds, are found in wastewater and are commonly dumped into nearby waterways, or even in cases where they are removed by scrubbers, the liquid from scrubbers is itself discharged into the regional water supply. Uranium mining and milling are developing within the Basin, with Indian and Bangladeshi operations increasing their activity. The World Bank has supported the Bangladeshi government’s plans for developing uranium extraction for export and energy generation (detail). Uranium deposits exist in the northeastern part of Bangladesh, the Khasi hills in Meghalaya, and also in the northwestern part of Bangladesh. Uranium mines like the Domiasiat uranium mine and mill in the Khasi hills produce enormous amounts of uranium tailings. Arsenic also occurs in the uranium ore, and is released, along with heavy metals like molybdenum and manganese in the tailings. The milling process uses acids and chemicals to dissolve the uranium, and about 90% of the radioactivity in the ore remains in the tailings. The health impacts of uranium mining are catastrophic, and well documented. Radiation from uranium mines located in the state of Bihar have been linked to genetic mutation and slow death among the more than thirty tribes living in the southern Bihar. 30,000 people from 15 villages in the vicinity of the tailings pond suffered from skin lesions and disease, cancer, tuberculosis, fertility loss, bone and brain damage, kidney damage, hypertension, disorders of the central nervous system, congenital deformities, insomnia, nausea, dizziness, and pain in the joints and abdomen. The focus by foreign investors and international aid on expansion of energy production in Bangladesh, particularly using natural gas, in recent years, will likely increase both the amount and the circulation of toxins within the basin. Increasing natural gas extraction can fundamentally alter aquifers and bring up water from deeper levels, and in the process, release arsenic and other toxins into water systems used for human consumption. Power production has its own toxic byproducts. Inadequate procedures for waste disposal, for example, lead to direct air discharges of sulphur and nitrogen oxides, and water discharges of copper from cooling systems, excess and unused fuels, lubricants, coolants and solvents. Power plants demand large amounts of water for cooling, which requires increased groundwater pumping - which can extract more arsenic from aquifers. Of equal or even greater significance is the fact that the power generated is primarily directed to industry use, which ultimately means increased toxic production. Natural gas is a feedstock for the agrochemical industry, with gas liquids providing about 70% of the feedstocks for ethylene (ethylene is the most basic petrochemical produced; trichloroethylene is a known carcinogen). Moreover, natural gas comprises 85% of the inputs for urea fertilizer production - in which some processes use arsenic oxide for separation and produces extremely hazardous arsenic laden effluent. International aid agencies project that approximately $4 billion of investment in natural gas power generation over the next five years are “required”, and this matter should be of gravest concern for immediate investigation. Urea fertilizer production, providing Bangladesh’s fifth largest export commodity, varies widely in its pollution intensity. There are some first order toxicity problems, however, which are generally associated with the industry, including the use of arsenic oxide and the production of arsenic discharge from at least one type of separation process, as just noted. Another source of carcinogens and other major toxins is the leather, or tanning industry which constitutes a substantial percentage of Bangladesh’s economy. The chemicals released from leather processing are well documented and include cyanide based oils and dyes, chromium salts and formaldehyde - all of which are carcinogenic, and the wastes that may be discharged include lead, cyanide, and sulfides. These chemicals are potentially major contributors to the unfolding health crisis in the basin - a reality suggested by innumerable instances, such as chromium contamination of drinking water supplies by tanneries in Mexico. In conclusion, it seems highly probable that the toxics crisis in the Bengal Basin is a broad based one involving many chemicals from multiple sources. We urgently call upon the Congress to support a thorough and swiftly executed program, to identify the specific sources of these toxins, their full manifestation in health and everyday life within the Basin, and potential solutions available. Such a program would surely involve those most affected throughout the Basin, as well as professionals and those in positions to expedite change. (End by reading quote, please) “All people have a right to a clean environment. Material wealth, such as the guarantee of food, employment, subsistence, education, and health, will not make human life worthwhile without having clean air, water, and land… Recent incidences of ammonia contamination of rivers by the Ghorasal fertilizer factory, trace metal contamination of soils by the Hazaribagh tannery, arsenic contamination of millions of tube wells, and lead contamination of air will become catastrophic in proportion if no mitigation measures are taken.” -Md. Khalequzzaman, Assistant Professor of Geology, Georgia Southwestern State University

Arsenic In Surficial Soils Of Eastern Bangladesh

Stuart Rojstaczer and Mohammed Riajul Islam, Division of Earth and Ocean Sciences, Center for Hydrologic Sciences, Duke University, Box 90230, Durham, NC 27708, USA

Heavy metals in surficial soil in eastern Bangladesh are analyzed in light of arsenic contamination of water resources. Sixty samples from fifteen different sections were collected and have been analyzed by ICP-MS. Arsenic is not enriched in the sol compared to typical values elsewhere. The relatively high levels of As at shallow depths are likely due to adsorption onto clay minerals and Fe and Mn oxides formed during intense chemical weathering. Arsenic is pervasive in all of the soils sampled and concentrations do not correlate with the presence or absence of arsenic contamination of groundwater. The absence of strong spatial variability in arsenic or significant elevated concentration indicates that levels of arsenic contamination in groundwater are geochemically controlled, not source controlled.

Arsenic Toxicity In Humans: A Health Problem Of The Millennium

Ratna Chatterjee, Department of Reproductive Medicine, UCL Hospitals, London

At least 30 million people in the Bengal Basin are affected with As poisoning. Acute As poisoning is lethal and is very rare apart from those arising from acetoarsenite factory. Most cases are due to chronic poisoning. The most important marker of toxicity is dermatosis, which was first documented in Calcutta by Saha (1984). However benign conditions with multiple organs damage including carrier state is common The estimated risk is at least 100 million. But the accurate statistics is unavailable. This is likely to be a rising problem since largely unsolved. It is likely to be a silent epidemic. The long-term risks including carcinogenic risks may be very high. The high mortality and morbidity associated with As poisoning due to short and long-term health hazards are still undefined (organ damage, cancer, and genetic hazards). The aim of this presentation is to discuss the magnitude of actual and potential health risks and define strategies aiming to circumvent them.

Evaluation Of Arsenic As A Reproductive Genotoxin Using Chemotherapy As A Model

Ratna Chatterjee, Department of Reproductive Medicine, UCL Hospitals, London

Arsenic is an established genotoxin (genetic poison) in animals and probably in humans. It can cause chromosomal and DNA damage. Such damage can cause miscarriage, infertility birth defects, malformed babies and even birth of babies with brain damage. There is also a future possibility of cancer in affected victims as well as the offspring’s of the subjects. We have data from cytotoxic drug model to show the potential effect of the drugs to cause sperm-DNA damage as a reproductive risk factor in subjects exposed to chemotherapy. Thus there is a possibility for a similar risk in a group of As-affected individuals such as infertility, birth defects, miscarriage and other pregnancy-related complications. In this presentation, I will present the data of male and female gonadal damage inflicted by cytotoxic drugs and extrapolate its relationship with As. This information will be also useful in understanding the potential materno-fetal problem and therefore clarify defining better reproductive health care of patients affected with arsenic poisoning.

Lead And Cadmium Levels In Blood Of Children Of Dhaka, Bangladesh

M. A. Wahed1, Marie Vahter2, Barbo Nermell2, Tanvir Ahmed1, M. A. Salam1 and V. I. Mathan

OBJECTIVE: Determine the blood lead (Pb) and cadmium (Cd) levels in children as an index of the exposure to these toxic elements in the environment.

Methodology: In total, 49 children were included. They were living in the Tejgaon industrial area (11), Mohammadpur (14), and Keraniganj (24). A group of 9 children from other parts of Dhaka city admitted in the CRSC of ICDDRB was used for comparison. Determination of Pb and Cd in blood was done by atomic absorption spectrophotometer (AAS) attached with graphite furnace. Blood was collected from antecubital vein after careful cleaning with swabs containing isopropanol in Venojectsâ tubes containing EDTA.

Results: The concentration of Pb (mean ± SD 176 ± 49 mg/L) in the children from 3 study areas together were significantly higher than those from hospital (mean ± SD 126 ± 126 ± 84 mg/L). Blood Pb levels in children from the Tejgaon industrial area (21.5 ± 51.8 mg/L) were significantly higher compared to children from Mohammadpur (153.1 ± 48.4 mg/L), Keraniganj (170.9 ± 36.0 mg/L), and hospital. All children from 3 study areas showed high blood Pb levels were higher in the children (mean SD ± 1.1 ± 0.6 mg/L) from the study areas than those from the hospital (mean ± SD 0.33 ± 0.31 mg/L). Cd levels were significantly higher in children from Keraniganj than all other areas.

Conclusion: Both Pb and Cd levels in the blood of children from high-risk areas are alarmingly high. These could be due to high lead in the environment from gasoline paints, ceramics, batteries, etc. High Pb in hospitalized children indicates general contamination in the Dhaka city. Young children are mostly exposed to Cd through inhalation of smokes and contaminated soils and dust from industrial emissions and sewage sludge. There appears to be differences in the extent of contamination in different high-risk areas and the factors responsible should be investigated. 1 International Centre for Diarrhoeal Disease Research, Bangladesh, GPO Box 128, Dhaka 1000, Bangladesh.

2 Institute of Environmental Medicine, Karolinska Institute, Sweden

Removal And Destruction Of Arsenic From Potable Water By Regeneratable Selective Ion-Exchange Resin

S. Mohanta, R. L. Clarke, B. J. Dougherty, Electrochemical Design Associates (EDA), Berkeley, California, USA

EDA has developed a selective version of Electrochemical Ion-Exchange (S-EIX) which will remove arsenic (As) from solution whilst ignoring competing ions and complexes.

The City of Albuquerque Water Utility (AWU), in New Mexico, USA has Arsenic present in the aquifer it uses to supply its customers. Some wells have already exceeded the current standard and have had to be taken out of service. In addition, there is a move by the regulatory bodies to reduce the permissible concentration of As from 50 ppb to between 5 and 20 ppb.

Electric Power Research Institute (EPRI), American Water Works Association Research Foundation (AWWARF), Public Utility of New Mexico (PNM), Albuquerque Water Utility (AWU) and CH2M Hill, supported a phased demonstration of S-EIX system of EDA at AWU’s facility.

The present paper will discuss the results of that demonstration. The results showed that the output concentration of the system could be less than 1 ppb with very low capital and operating costs.

The method can be adapted to treat water in a pumping station or tube-well or a home filtering system and some of these concepts will also be discussed. The resin can be regenerated by a simple innocuous chemical method.

AWU’s Coranado No 2 Plumping Station

Development And Field Testing Of Arsenic-Nush Exchange System For The Selective Removal Of Arsenic From Potable Waters

S. Mohanta1, R.L. Clarke1 & D. J. Clough2 1 Electrochemical Design Associates (EDA), Berkeley, CA 94701, USA. 2 Magnesium Elektron Industries, 500 Point Breeze Road, Flemington, New Jersey 08822, USA The presence of arsenites and arsenates in ground waters in the Indian subcontinent are of considerable concern (1). Recently in the United States of America, a successful study was performed on such contaminated ground waters in the New Mexico basin. We carried out the study (2), sponsored by the Electric Power Research Institute and the American Water Works Association.

Originally the system was designed for operation by a large water utility such as the Albuquerque water works. In this case the ion exchange system could be electrochemically forced to adsorb the arsenite/arsenate ions onto its surface. In this mode we were able to remove arsenic anions from 70 ppb to less than 1 ppb. Current reversal allowed us to remove the arsenic into an alkaline concentrate leaving the ion exchange media ready for the next adsorption cycle.

In the latest development called the Arsenic-nushâ process we use the natural affinity of the ceramic for arsenic anion to strip and hold the arsenic from water being pumped through the media. Initially we want to use a practical system that can be used at the individual hand pumped level. The Arsenic-nushâ system is a cartridge type ion exchange filter for point use application. It is meant to protect householders using tube wells in contaminated ground water situations. We are developing this technology especially for the Bengal Basin, mindful that it must be safe, locally maintained and inexpensive.

The key part of the science is the ability of the specially prepared ceramic powder to selectively remove arsenic while ignoring other anions such as sulfate, chloride, and carbonates and cations such as sodium, calcium and iron. The ceramic is not a water sterilizing media nor does it remove by MEI. It is regulated as nom hazardous under the auspices of EPA, OSHA and DOT and FDA (Food and Drug Administration, US Govt.) approved material.

A second feature is the arrangement in the cassette that allows the water to flow through a material of relatively high surface area (low particle size) at an acceptable rate. The capacity if an ion exchange medium is a function of the surface area of the particles, the numbers of ion exchange sites and the affinity of the medium fort the target ions. With concentration of arsenic in the parts per billion the contact of the water with the unexposed medium is critical. The cassette will require replacement at a timely interval and the unit recycled. Removal and replacement of the cassette by the householder or pump operator assumes that the arsenic captured by the cassette is held fast and the unit stable for storage and transportation. Such is the case with the Arsenic-nush system.

The media is cleansed of arsenic by treatment in a specially designed unit, which will be under the control of trained technicians in the local area. Cleaned units will have a chemical tag that indicated they have been treated and are ready for reinsertion in the tube well. Although the ceramic material is inexpensive, recycling has some important features.

1. Control over the disposal of arsenic is maintained 2. Control over the replacement of the cartridge is established

3. Water quality with respect to taste and acceptability is not disturbed

4. Recycling cuts initial equipment costs to the minimum

The Process

Assuming the cassettes for a tube well are made from plastic pipe and porous materials filled with the ceramic ion exchanger, we have a target price of $10-20 (or 500 to 1000 taka, 400 to 900 Rs.) each. Each unit will be capable of removing 2g of arsenic with output level well below 50ppb. The units should be capable of recycling for several years if the desorption process is carried out at a properly designed station. The arsenic recovery from the cartridges to useful form is possible with EDA technology.

For large applications such as municipal water works, the process of adsorption and desorption is carried out on site as originally designed in the Albuquerque work. Examples and details of this work will be presented.

* EDA or Electrochemical Design Associates is a technology and design company with various technologies such as, (a) groundwater treatment for Arsenic and Chromium, (b) soil remediation for organic as well as inorganic contaminants, (c) resource recovery such as etchant regeneration, chromic acid generation, and (d) self contained high efficiency aerobic digestion of sewage.

References

1. New York Times, November 10, 1998

2. Removal and Destruction of Arsenic from portable water, by EDA personnel, submitted to Albuquerque Water Works.

Ligand Reaction Based Arsenite And Arsenate Removal Technology From Bengal Groundwater

S. Mohanta*, C. Butler**, R. L. Clarke*, B. J. Dougherty*, and S. R. Clarke, , Electrochemical Design Associates (EDA), Berkeley, California, USA

* EDA Inc., 829 Heinz Street, Berkeley, CA 94710 USA

** Luxfer Group, The Victoria, Harbour City, Salford Quys, Manchester, England M5 2SP

EDA and Luxfer Group have developed a ligand reaction based technology for removal of arsenic in Arsenite, As (III) and Arsenite, As (V) forms from groundwater. Patents have been applied for. Luxfer Group is currently developing an easily useable device to effectively treat contaminated wells in the Bengal Basin. Traditionally, ion exchange and activated alumina adsorption methods have been proposed to remove arsenic in the form of arsenate. They suffer from a few technological disadvantages, which include:

(a) Arsenite that is more predominant in anaerobic groundwater condition is non-ionic and must be oxidized. This leads to two-stage process.

(b) The loading capacity is not very high leading to non-compact and expensive systems

(c) The background ions often compete with reaction sites reducing the loading capacity even further

The ligand based ceramic technology circumvents all these deficiencies. Our test results show that:

(a) The media reacts with both arsenite and arsenate

(b) The loading capacity is very high. One kilogram of the media can remove 45 grams of As (III) or 7.5 grams of As (V) at 1000 ppb level of Arsenic

The test results of the technology in Bengal surrogate water and some product concept and economics will be presented.

A Clearinghouse for Geographic Information from the Bengal Basin

Drs. Remi Kempers, Hydrogeologist, Highlander Consult, Amsterdam, The Netherlands

A Clearinghouse for Geographic Information from the Bengal Basin: The Arsenic Topic as Supercharger? Geographical information can serve as an important resource. Associating data sets with a location seems to operate cohesively, bringing together users from different disciplines with a variety of applications. Cooperation leads to better, or cheaper, task implementation. Location information permits the integration of widely differing data bases. Thematically oriented files can be presented graphically, as maps. In turn, these will be major tools in managing the mitigation of the arsenic problem. The need for more awareness of dealing with geographic information is obvious. In Bangladesh the EGIS institute has developed already a number of programs and GIS- projects. Results of these studies are only known to insiders and hardly communicated towards the outside world. Availability of results on Internet are slowly progressing. More effort should be put into attempts to involve more disciplines in GIS-projects and data base building. An important factor in these is the standardizing of the content and format of geographic information metadata. In this way geographical information is of potential use to a much larger audience than that it is now. However, the first step in intelligent use and re-use of geogrphical information is knowing what data is available, where, in what format, accessible under what conditions and at what costs. Paper by Drs. Remi Kempers, Hydrogeologist, Highlander Consult, Amsterdam, The Netherlands

Application of Activated Alumina-Based Arsenic Removal Units Anirban Gupta, Pratip Bandyopadhyay, Ranjan K. Biswas, Swapan K. Roy and Morshed Alam Department of Civil Engineering, Bengal Engineering College (Deemed University) Howrah – 711 103, India Abstract Vast areas of Bangladesh and West Bengal (India) are facing problem with high concentration of arsenic in their ground water that is used for drinking. Any long- term measure to supply safe surface water to the people in the arsenic-prone areas may be a capital-intensive venture, which will also need significant time to implement. The need, therefore, arises for suitable short-term (interim) measures for provision of safe drinking water sources. The arsenic-contaminated water from tubewells (hand-pumps) can be treated to make it fit for drinking. Among the candidate technologies for treatment, adsorption on activated alumina (AA) shows much promise. Based on our laboratory as well as field experiments, it was observed that (i) activated alumina can adsorb both As (V) as well as As (III), though the sorption of As (V) is more efficient, (ii) activated alumina can be suitably regenerated for reuse, once its capacity is exhausted, (iii) the treated water becomes more palatable as the iron content is also brought down, (iv) simple treatment units can be designed with AA for application in domestic as well as community-level, (v) the service life of the units in a single cycle is reasonable for practical application. The service life of domestic units was found to vary between eight months to two years in a single cycle, whereas the same for community-level units varies from eight months to eighteen months depending on the raw water arsenic concentration and also the daily intake through the Units. The AA bed in the domestic units is suitably housed in a specially designed bag for replacement during regeneration after it gets exhausted. For regeneration of the AA bed of the domestic units, it is suggested to be conducted in a central location and not in each household. However, the hand pump- attached units are designed in a way such that regeneration can be undertaken in situ. For regeneration, commercially available hydrochloric acid and caustic soda are needed and the local persons can be trained for this purpose. The spent regenerant contains high concentration of arsenic, and should not be disposed of in open drains or surface water bodies. A protocol has been developed to contain the arsenic in a limited volume of sludge, which can be subsequently subjected to cement-based stabilization. The occasional backwashing, which the hand-pump units should be subjected to for removal of the deposited iron flocs from the bed, would generate a backwash that contains higher concentration of arsenic. It has been found that more than 90% of the arsenic is associated with iron flocs and a sand bed is provided by the side of the Unit to arrest these flocs and the output through the bed contains low arsenic concentration. The sand in the bed along with the accumulated iron flocs (containing arsenic) may subsequently be subjected to similar cement-based stabilization. Such hand pump-attached units have been installed in ten places, which are working successfully. In four places of North 24 Parganas district (West Bengal), the beneficiaries formed a committee to take care of the operation and maintenance of these Units for which they are collecting a water tariff from the users. In Nadia district (West Bengal), a voluntary organisation is taking care of the Units. These units can also be dismantled and installed elsewhere, if alternative source of safe water is subsequently arranged by other means. It is felt that the activated alumina- based arsenic removal units may serve effectively to provide safe water to the people in the arsenic-prone areas, till any long-term and permanent measure can be implemented.

EDA's Arsenic Removal Technology

Dr. Samaresh Mohanta

This study showed that under the laboratory conditions the EDA’s proprietory ceramic media absorbs Arsenic extremely well and preferentially in the presence of various tramp ions as would be present in Bengal Basin ground water. There is no foreseen scientific and/or manufacturing hurdle for this technology. A study was initiated to determine the functional applicability of a Ceramic Media to remove Arsenic from Bengal Basin Groundwater. The primary objectives of this study were: Determine the effect of background ions present in the water, namely iron, phosphate and sulphate, on the Arsenic removal capacity of the media Determine the loading capacity of the media in packed bed configuration Build and test a prototype for tubewell application for Bengal Basin Compare EDA media with activated alumina in this application A typical tubewell in Bangladesh Background shows a typical village pond and a residence This report describes the laboratory work carried out and the results obtained thereby. The principal conclusions of this work are: The interference of background ions: The interference’s of the following background ions were tested: iron, bicarbonate, hydronium, phosphate and sulfate. The concentration levels chosen were twice that of the maximum present in 13 of the Bangladesh water samples. None of these ions showed any influence on the effectiveness of removal of Arsenic by EDA-media. The loading capacity (defined by wt. % of Arsenic that can be absorbed) of the media in the three surrogate water was found to be 1.3%-1.5% in a column test. Activated Alumina was not at all effective in removing Arsenic (III) or it needed longer contact time and bed depth in the packed bed column test. A unit showing the main working principles of a filter has been produced. This is delivering about 8 lpm at a head of 13.5 in. water. The removal of Arsenic is also demonstrated in this unit. The output of the device was analyzed in an outside lab and was found to contain non-detect level of Arsenic. Detection limit was 5 ppb. Unit size is 2ft. high and 1 ft-square. The test on this unit is continuing. A paper study on manufacturing cost showed that the commerciallization of the device is very feasible. A patent has been filed. Based on these conclusions, there is no foreseeable technical or engineering impediment to the use of this process for arsenic removal applications in the Bengal Basin. Moreover, given that the paper study confirmed our working assumptions on manufactured cost, commercialization of this technology is strongly recommended.

Chronic and acute arsenic poisoning through drinking water Dr. Ratna Chatterjee, UCL London

Chronic and acute arsenic poisoning through drinking water: impact on male and female reproductive health and future children. River Water Quality: The Source of Arsenic Free Drinking Water in Bangladesh Islam, Md. Riajul.1, Islam, Muhammad, Anwarul.2 Rojstaczer, Stuart*1 Islam, Md. Riajul Islam, Muhammad Anwarul 2. Rojstaczer, Stuart

1. Division of Earth and Ocean Sciences Duke University Box 90227 Durham, NC 27708-0230, U.S.A.

2. Department of Geology and Mining,University of Rajshahi Rajshahi 6205, Bangladesh

Recently, attention is focused on extensive arsenic contamination of groundwater in Bangladesh but surface water bodies throughout Bangladesh are subject to potential water quality hazards associated with metals due to both intense chemical weathering and anthropogenic activities. The issue of surface water quality is very crucial since the Government has suggested that inhabitants use surface water in areas where groundwater has been severely affected by arsenic. The main objectives of this study are to evaluate dissolved inorganic materials including As in major rivers and to identify the environmental factors that control their hydrogeochemistry. The geography of Bangladesh is dominated by the three great rivers Ganges (Padma), Brahmaputra-Jamuna and Meghna and a dense network of branches, distributaries and connecting channels which is estimated to be about 24,000 km (Rashid, 1977). The stratigraphic succession of Bangladesh is composed of Tertiary sediments, occasionally covered by Quaternary overburden. Sandstone, siltstone, shale and claystones are the main rock types existing all over the country. In the present study, 16 water samples were collected from the three major rivers - Padma (Ganges), Brahmaputra-Jamuna and Meghna and from other two branches - Mahananda and Buriganga during the flood season and analysed by IC and ICP-MS.

Concentrations of major nutrients, NO3-N, PO4-P and heavy metals are much lower than the WHO-(1996) guidelines. Arsenic concentration ranges in between 4.6 - 4.9 ppb in water from all the major rivers in Bangladesh. The more or less constant concentration is somewhat surprising, as flow volumes differ dramatically and dilution of dissolved constituents should increase downstream. The lack of dilution suggests that concentration of As is at saturation for the geochemical conditions present in the river water. If this is so, concentration during the dry season would likely be similar to that observed in this samples and river water, aside from pathogens, should be safe for drinking year round. We will be testing river water during the dry season in the spring of 2000. The non- filtered and acidified water samples show higher concentrations of metals which indicate that the metals released due to intense chemical weathering have co-precipitated and/or adsorbed on to the colloidal clay fractions and organometalic complexes which were filtered out by 0.45 micrometer net. This difference also suggests that dissolved concentration of metals are at saturation.

Arsenic in drinking water and skin lesions

Mahfuzar Rahman, MD, Ph.DA POSTER

Arsenic in drinking water and skin lesions

Mahfuzar Rahman, MD, Ph.D, Division of Occupational and Environmental Medicine Faculty of Health Sciences Linköping University S-581 85 Linköping, Sweden

Chronic arsenic intoxication from drinking water as contaminated from geological sources has caused a devastating health crisis, in Bangladesh. A similar situation can be observed not only in Bangladesh, but also in some other parts of the world. Skin lesions are the hallmark of high exposure to arsenic and pose a public health problem in Bangladesh. A cross-sectional study was performed by door to door visits, interviewing families with arsenic exposure and skin lesions. We interviewed 1146 individuals irrespective of age and sex who had at least one sign of arsenical skin lesions, i.e., keratosis, leocomelanosis or melanosis. The mean arsenic level in their drinking water was 144.4 mg/L (non-detectable limit to 4727 mg/L) and the sex ratio was 1.5: 1 (men and women). Clinical examinations of the 1146 subjects who all had some typical skin lesion, in term of melanosis (99/100) and keratosis (66.8/100). This study shows a higher percentage of arsenic skin lesions in men than women. These skin lesions are an alarming sign of high arsenic exposure. There is an urgent need for a technical solution to provide good quality drinking water and requests for urgent remedies, especially regarding future skin cancer.

Mahfuzar Rahman, MD, Ph.D Environmental exposure to arsenic and nonmalignant health effects.

ORAL Environmental exposure to arsenic and nonmalignant health effects Division of Occupational and Environmental Medicine, Faculty of Health Sciences, Linköping University, S-581 85 Linköping, Sweden

Abstract A series of studies concerning environmental exposure to arsenic and some novel chronic health effects of this element, namely diabetes mellitus, glucosuria and hypertension. Substantial prevalence of the well-known skin manifestations of arsenic ingestion was also found to occur as a result of environmental exposure through drinking water. A cross-sectional study was carried out in Bangladesh, where a fairly large part of the population is exposed to inorganic arsenic in drinking water. The prevalence of diabetes mellitus among subjects with keratosis (n = 163) was compared with unexposed subjects (n = 854); keratosis was considered to be a definite sign of exposure. A dose-response relationship was found between categories of time-weighted arsenic exposure (mg/L in drinking water) and the prevalence of diabetes mellitus (p < 0.001), and the crude overall prevalence ratio amounted to 4.4. Despite the lack of detailed individual exposure data and information on potential confounders other than age, sex, and body mass index (BMI), the association seems strong enough to support a causal relationship, because the adjusted overall prevalence ratio was 5.9 (95% confidence interval 2.9-11.6). One study from Bangladesh indicated a significantly increased risk of hypertension in connection with exposure to inorganic arsenic in drinking water (1481 exposed and 114 unexposed subjects). The overall crude prevalence ratio of hypertension amounted to 1.7, and the adjusted (for age, sex, and BMI) ratio was 1.9 (95% confidence interval 1.0-3.6). A significant trend in risk (p << 0.001) was observed between an approximate time- weighted mean exposure to arsenic, considered in milligrams per liter or milligram-years per liter, which strengthens the possibility of a causal association. One of the other studies included 1481 exposed individuals, 430 exhibiting keratosis showed a somewhat higher prevalence rate of skin lesions in males (31%) than females (26%) due to chronic arsenic toxicity. The crude overall prevalence was 29% in the studied villages, and there was a distinct dose-response relationship between arsenic concentrations in drinking water and skin lesions (p < 0.01). A clear dose-response relationship was also observed between arsenic exposure and glucosuria for subjects both with and without skin lesions (p < 0.01). The possibility of using the skin lesions for initial screening for glucosuria was considered. However, the appearance of dermatological signs of chronic arsenic toxicity proved to be a poor marker in this respect, because glucosuria also occurred in the absence of skin lesions. Overall, the results of these studies provide evidence that arsenic exposure may play a role in the development of diabetes mellitus, however, the mechanism underlying the ability of inorganic arsenic to induce these disorders is still unclear. Various sources of exposure should be taken into consideration in further confute or refute the indicated effects of arsenic. POSTER Arsenic in drinking water and skin lesions Mahfuzar Rahman, MD, Ph.D Division of Occupational and Environmental Medicine, Faculty of Health Sciences, Linköping University, S-581 85 Linköping, Sweden Abstract Chronic arsenic intoxication from drinking water as contaminated from geological sources has caused a devastating health crisis, in Bangladesh. A similar situation can be observed not only in Bangladesh, but also in some other parts of the world. Skin lesions are the hallmark of high exposure to arsenic and pose a public health problem in Bangladesh. A cross-sectional study was performed by door to door visits, interviewing families with arsenic exposure and skin lesions. We interviewed 1146 individuals irrespective of age and sex who had at least one sign of arsenical skin lesions, i.e., keratosis, leocomelanosis or melanosis. The mean arsenic level in their drinking water was 144.4 mg/L (non-detectable limit to 4727 mg/L) and the sex ratio was 1.5: 1 (men and women). Clinical examinations of the 1146 subjects who all had some typical skin lesion, in term of melanosis (99/100) and keratosis (66.8/100). This study shows a higher percentage of arsenic skin lesions in men than women. These skin lesions are an alarming sign of high arsenic exposure. There is an urgent need for a technical solution to provide good quality drinking water and requests for urgent remedies, especially regarding future skin cancer.

W.G.Burgess1 and K.M.U.Ahmed:The variability of arsenic in groundwater of southern Bangladesh - keys and constraints for sustainable development W.G.Burgess1 and K.M.U.Ahmed2

The variability of arsenic in groundwater of southern Bangladesh - keys and constraints for sustainable development W.G.Burgess1 and K.M.U.Ahmed 2London

Dhaka Arsenic in Groundwater Project

1 Dept. Geological Sciences, University College London, Gower St., London WC1E 6BT, UK [email protected]

2 Dept. Geology, University of Dhaka,Dhaka, Bangladesh [email protected]

Arsenic is a widespread pollutant of groundwater in southern Bangladesh. Response to the arsenic threat must take account of the nature of its occurrence, and the scale and patterns of variability that are evident spatially, with depth and in time. Hydrochemical relationships have demonstrated that chemically reducing conditions favour the release of arsenic from sedimentary iron oxyhydroxides which are the source of the pollution. How is the source distributed within the alluvial sediments? What is the manner of its movement to tube-wells? Detailed observations of the spatial variability of arsenic in pumped groundwater, and depth profiles of arsenic in groundwater, pore-water and aquifer sediments, have been used to develop a conceptual model of arsenic movement to tube-wells. Preliminary numerical models reproduce the variability observed spatially and with depth. The results constrain answers to the questions on how successfully tubewell placement, design and pumping regime can be managed to minimise the arsenic concentrations in pumped groundwater, how arsenic concentrations may change with time, and the effectiveness of monitoring. These are the key issues for sustainable development of groundwater in southern Bangladesh.

Dr. Barin Chatterjee: A Geotechnical Approach To The Problem In Bengal Basin A Geotechnical Approach To The Toxicity Problem In The Bengal Basin

By Barin Chatterjee

Before arriving to any possible solution to the problem, it should be known why this contamination problem is concentrated in the Bengal basin, what is the source and does it occur in any correlatable way ? The present endeavor is to throw some light on a possible correlation from the geotechnical observation. In course of working in the lower Damodar basin for its endemic flood problem, it could be observed that there are at least two mappable arcuate micro-relief bands, almost swerving like bird’s track. These bands could be picked up towards the upper part of the delta by means of exaggerating the vertical scale with respect to the horizontal scale while contouring at 1 m interval on a 1:250,000 scale. By subsequent geotechnical analysis with undisturbed soil samples collected in a grid pattern, it could be established that the micro-relief zones represent higher values of pre-consolidation pressure to the tune of 3 kg/sq. cm in comparison with the background value of 0.9 kg/sq. cm. The topography being almost flat, this led to infer zones of initial depth of burial followed by subsequent squeezing up of sediments ( Chatterjee,B : Geotechnical aspect of endemic flood problem in the lower Damodar basin, West Bengal, India ; VI International Congress of the Association of Engineering Geology, IAEG,1990 published by Balkamara, Rotterdam, ISBN 90 61911303, pp. 2785- 2790). Such deposition and uprising, basically a long drawn and contemporaneous process, are manifested as drape over reefs along the palaeo-shore line ( Morgan, J.P, 1968 ; Mud lump : Diapiric structures in Mississipi delta sediments; Mem.8, Am.Assocn.Pet.Geologists, Tulsa, Oklahama, pp. 145-161 ). Due to rapid deposition of denser mouth bar sand over the less denser marine clay in the palaeo-shore line areas, the differentially weighted clay subsequently gets squeezed up in the form of Diapiric type of intrusion. In the upper part of the delta, it takes the shape of micro-relief on the surface, while down the slope, in the subsurface, it causes barriers to the path of subsurface infiltration, resulting in localized pockets of toxic ground water aquifers. Due to non- existence of any surface expression, it is very difficult to identify such zones in the down- delta region. As ground water is now being extensively used for drinking and irrigation purposes, it calls for identification of such zones by a systematic extensive geotechnical investigation , keeping in view the possible palaeo-shore lines.

Chemotherapy as a model to understand arsenic toxicity in human reproductive Dr. Ratna Chatterjee

Chemotherapy as a model to understand arsenic toxicity in human reproductive and feto- maternal health

Abstract/Paper is under preparation

The Problem of the Century

Dr Ratna Chatterjee Department Of Reproductive Medicine UCL, London

Arsenic and reproductive and sexual health issues: what do we know about it? The Problem for the century.

NATURALLY OCCURRING ARSENIC IN SANDSTONE AQUIFER WATER SUPPLY WELLS OF NORTHEASTERN WISCONSIN

Rebecca S. Burkel and Richard C. Stoll

NATURALLY OCCURRING ARSENIC IN SANDSTONE AQUIFER WATER SUPPLY WELLS OF NORTHEASTERN WISCONSIN Rebecca S. Burkel and Richard C. Stoll Rebecca S. Burkel is the District Environmental Coordinator for the Wisconsin Department of Transportation, Division of Highways, 944 Vanderperren Way, Green Bay, WI 54304. Rebecca is a graduate of the University of Wisconsin Green Bay with a BS (chemistry) and a MS (environmental science) degree. Richard C. Stoll is the District Hydrogeologist for the Wisconsin Department of Natural Resources, Lake Michigan District office in Green Bay, Wisconsin. Rick is a certified Groundwater Professional (CGWP #457) with the National Groundwater Association, a Certified Professional Geologist (CPG #9157) with the American Institute of Professional Geologists, and a State of Wisconsin Professional Geologist (#38). ABSTRACT NATURALLY OCCURRING ARSENIC IN SANDSTONE AQUIFER WATER SUPPLY WELLS OF NORTHEASTERN WISCONSIN

Rebecca S. Burkel and Richard C. Stoll

The EPA maximum contaminant level (MCL) of 50 Fg/L for arsenic was exceeded in 86 of 2125 water supply wells sampled over a broad geographic range in parts of Brown, Outagamie and Winnebago Counties, Wisconsin. The hydrologic and geochemical properties of the area were examined and the source of arsenic determined to be natural. Groundwater collected from two geologic formations, the St. Peter Sandstone and the overlying Platteville/Galena Dolomite, were found to be the principal sources of the elevated arsenic concentrations. These two formations supply a large portion of eastern Wisconsin private wells their drinking water. Three wells were found within Outagamie County to have an unusually low pH. Results suggest that the cause of the low pH in these wells is of natural origin induced by the oxidation of iron sulfide minerals. In this reaction iron sulfide minerals are oxidized forming sulfuric acid causing a low pH and a high concentration of various metals to leach from native rock formations into the water supply. Based on the data gathered from this study an arsenic advisory area for both Outagamie and Winnebago Counties was designated. Guidelines were developed for well drillers and owners constructing new wells within the advisory area to reduce the likelihood of arsenic presence in the water supply. Fifteen wells containing arsenic exceeding the MCL were successfully reconstructed or new wells were constructed based on the guidelines developed. These constructions substantially reduced arsenic levels in the well water supplies.

INTRODUCTION Arsenic (As) contamination in water supplies in Winnebago County, Wisconsin, was first identified in two different locations in 1987. Following this the Wisconsin Department of Natural Resources (WDNR) initiated a study in 1991 to investigate the occurrence of As in private wells in Outagamie and Winnebago Counties. The study was expanded to include parts of Brown, Marinette, Oconto and Shawano Counties, Wisconsin, following the results of investigation in Outagamie and Winnebago Counties. The objective of the study was to determine the source and lateral and vertical distribution of As occurring in groundwater and geologic formations. The study results were used to develop special well casing and well construction criteria for new wells in affected areas Arsenic enters the environment through natural processes or via human activity (Eisler, 1988). Natural processes that influence the presence of As are volcanic emissions and weathering of arsenic-containing rocks with minerals such as arsenopyrite (FeAsS) (Eisler, 1988). Currently, the drinking water standard for total As is 50 Fg/L, as established by the Safe Drinking Water Act (SDWA) in 1986. Geology of Brown, Marinette, Oconto, Outagamie, Shawano and Winnebago Counties, The Study Area There are five principal geologic units beneath the glacial overburden in Brown, Marinette, Oconto, Outagamie, Shawano and Winnebago Counties, Wisconsin. The Platteville/Galena Dolomites overlie the Saint Peter Sandstone. Beneath the sandstone are the Prairie du Chien Dolomites and the Cambrian Sandstones. The basement consists of crystalline Precambrian rocks. The overlying Platteville/Galena Dolomites are composed of sandy-gray to bluish-gray dolomite with fine to medium grained sandstone near the base (Olcott, 1966). The formation generally yields little water to wells (LeRoux, 1956). However, in certain locations sufficient quantities of water exist in joints, bedding planes and fractures to furnish some private wells. The St. Peter Sandstone is a productive water-yielding unit. It consists of fine to coarse-grained dolomitic sandstone (LeRoux, 1957). The St. Peter Sandstone rests on the Prairie du Chien Group filling in low areas but it is absent on the Prairie du Chien highs (Olcott, 1966). Water yields from the St. Peter Sandstone are limited by the presence of shale and by the limited thickness of the formation. The Prairie du Chien is a relatively unproductive water yielding unit. The Prairie du Chien Group consists of dolomite with thin layers of white sandstone and green shale (Olcott, 1966). The upper surface of the Prairie du Chien is highly irregular (Olcott, 1966). A limited amount of water is found in fractures, joints, and bedding planes (Olcott, 1966). The Cambrian sequence rests on the irregular and highly eroded surface of the Precambrian rock (Olcott, 1966). The Cambrian System is made of fine to coarse grained sandstone. These sandstones are a major source of groundwater especially for municipal wells. The Precambrian crystalline rocks are composed primarily of granite and except for fractures are generally impermeable. METHODOLOGY Well Water Sample Collection and Analysis Initial water samples were collected by the WDNR following the guidelines set in the WDNR Groundwater Sampling Procedures Field Manual and the WDNR Groundwater Sampling Procedures Guidelines both developed by Lindorf, Feld, and Connelly (1987). These were later supplemented by a private-well- owner sampling program. All samples were collected from a cold water tap situated prior to any in-line treatment device (e.g. a water softener or filter). Samples were collected after flushing the water supply tap for three to five minutes or a couple of minutes after the pump started running. This procedure identified in WDNR Groundwater Sampling Procedures Guidelines developed by Lindorf, Feld, and Connelly (1987) was used to ensure the water sample represented in situ groundwater and not water standing in the pipes. All samples were collected, preserved with 2.5 ml/ 35% (8N) HNO3,to a pH of less than 2 and labeled in appropriate 250 mL sample containers supplied by the Wisconsin State Laboratory of Hygiene (WSLH). Samples were analyzed for As by high temperature graphite furnace atomic absorption method, 3113B in the Standard Methods for the Examination of Water and Wastewater, 17th Edition, (1989). The methods had either a 2 Fg/L or a 3 Fg/L lower detection limit for As. All sampled well locations were plotted on 7.5 minute USGS topographic maps or keyed with a global position system (GPS) for digitizing into a geographic information system (GIS). Multiple information layers including land net, railroads, trunk highway network, local roads, hydrology, bedrock geology, glacial geology, potentiometric surface and all known point and non- point potential groundwater contamination sources were created for all of northeast Wisconsin. This information was analyzed with respect to As contamination utilizing PC ARC/Info and ARC View GIS software. Geophysical Well Investigation Methods - Inflatable Packer Tests Packer tests were used to isolate and sample specific subsurface water-bearing zones within wells and thus to identify potential subsurface horizons with poor water quality. Two wells, 1 and 4, were chosen for packer testing, (Figure 1). Both wells were selected based on their significant depths and the elevated As concentration of their water. See Figures 3 and 4 for well 1 and 4, respectively, lithology and construction. Furthermore, the family consuming water from Well 1 was informed by their physician that they exhibited symptoms associated with chronic As poisoning. Wells 1 and 4 are located about 24 km from each other. To minimize costs, packer test intervals of 9.1 and 4.6 m (Wells 1 and 4 respectively) were selected to best define vertical variations in As concentration throughout the entire well column with the fewest number of packer tests. Each Packer interval was pumped for approximately 10 minutes at 37.8 L/min so that a representative water sample could be obtained from each interval. The integrity of the packer assemblies were monitored using water level indicators throughout the packer tests to verify that the water sampled during the test was actually collected from within the designed packer interval. Samples were collected only from those packer tests with confirmed packer seal integrity or those that showed little fluctuation of water level measurements during pumping. However, due to the type of packer assembly used at Well 4, the integrity of the bottom packer seal could not be monitored. The bottom packer may not have sealed when sampling took place nearest the bottom of the well column. The bottom 6.1m of the well was filled in with sediment. Sediment and colloidal material clogged the pump and was incorporated into the sample that was analyzed. Well 1, at packer interval 10, the sample was collected after the pressure tank. The owner required temporary reservice of water. The pressure tank had a torn bladder. This may allow for outside contamination. Also, the water level indicator showed a leaking top packer at interval 10. This may have allowed for contaminated water from the upper portion of the well to drain into the area being packed off. All other samples from Well 1 were collected directly from the packer assembly, prior to the pressure tank. The water samples from packer test wells were collected according to WDNR guidelines. Packer test water samples were collected from a brass tap located directly above the packer assembly prior to disposal to a holding tank. Water samples from each packer were tested for field pH and field temperature. The water sample was then filtered using a 0.45 micron filter prior to being sent to the WSLH for analysis of As, cadmium (Cd), copper (Cu), manganese (Mn), and zinc (Zn). The parameters As, Cd, Cu, Mn and Zn were selected based on the elevated levels found in the original well samples . All samples were collected, preserved with 2.5 ml/ 35% (8N) HNO3, to a pH less than 2 and labeled in appropriate 250 mL sample containers supplied by the WSLH. Samples were analyzed by high temperature graphite furnace atomic absorption methods: and inductively coupled plasma, following procedures 3113B and 3120, from the Standard Methods for the Examination of Water and Wastewater, 17th Edition (1989).. RESULTS and DISCUSSION Private Well Arsenic Levels The distribution of water well As concentrations in Brown, Marinette, Oconto and Shawano Counties is markedly different from Outagamie and Winnebago Counties. Arsenic exceedances do not occur in Marinette and Oconto Counties while limited exceedances occur in part of Brown County. Outagamie and Winnebago Counties exhibit wide spread As exceedances over a 8.0 km area. Winnebago County had 23 of 827 wells sampled that exceeded the SDWA MCL for As while Outagamie County exhibited 45 of 1116 wells over the MCL (Table 1). Low pHs ranging from 2.5 to 3.8 were documented for 3 wells in Outagamie County. Sampling in Brown County was conducted where wells intercept the upper St. Peter Sandstone similar to those in Outagamie and Winnebago Counties. The As problem appears to be a localized problem in parts of Brown County where 18 of 76 wells sampled exceeded the SDWA MCL. Seventeen of these wells exceeding the MCL are located within the same square 2.6 km or township, range and section. This enclave of impacted wells is surrounded by an area of municipal water service such that additional nearby water sample collection locations are limited. However, one well with As exceeding the MCL is located about 3.2 km away from the 17 other As-impacted wells in Brown County. Each of these wells draws water from the upper St. Peter sandstone. One well with both a field pH as low as 3.1 and As over the MCL is documented in Brown County. The sample information for Shawano, Oconto and Marinette Counties indicate this more northern group of counties is much less likely to exhibit As-related drinking water problems. While the sampling conducted in these counties was also along the St. Peter Sandstone subcrop and conducted similarly, there were no SDWA MCL exceedances or pH problems. Wells with elevated levels of As were found principally in areas where St. Peter Sandstone is present, based on existing bedrock geology maps (Figure 2). This is where the St. Peter Sandstone is the predominant aquifer supplying private wells. There are, however, some areas where wells with elevated As concentrations lie west of the mapped St. Peter Sandstone trend. This is unexpected if the St. Peter Sandstone is the primary source of naturally occurring As in the groundwater. The following are potential explanations for this: (1) the sandstone lenses of the Prairie du Chien or the older underlying sandstone of the Cambrian formation may also contribute As to well water rather than only the St. Peter Sandstone formation; (2) some of the St. Peter Sandstone subcrop contacts shown on the bedrock map for this area are inferred. The subcrop was inferred because there was not enough data to map it accurately. These inferred areas correspond to the areas where wells with elevated As concentrations exist to the west of the mapped subcrop; (3) localized westward shallow groundwater flow, impacted by As, may move As down gradient away from the regional divide to where it would not normally be suspected. The regional groundwater divide parallels much of the St. Peter Sandstone subcrop expression. Well 1 - Water Quality Well 1 was first sampled in 1992, due to the owners complaint of an iron (Fe) problem. The well was sampled for both Fe and As because the well was located near the St. Peter Sandstone trend. Initial test results revealed a high Fe concentration (87 mg/L) and an As concentration of 1200 Fg/L, the highest As concentration recorded at that time in a private water supply well in Outagamie County. Two months later a follow-up water sample was collected and analyzed for As, Cd, chloride (Cl), chromium (Cr), conductivity, pH, alkalinity, barium (Ba), calcium (Ca), Cu, Fe, Mn, sodium (Na), Zn, hardness, lead (Pb), nitrate+nitrite-nitrogen, selenium (Se), silver (Ag), sulfate, total solids, field pH, and field temperature. Both the field pH and lab pH indicated normal ranges for groundwater from 6 to 8 (standard units). Chloride, Cr, conductivity, alkalinity, Ba, Ca concentrations were were 4.0 mg/L, 8.2 Fg/L, 743 umhos/cm, 60 mg/L, <40 Fg/L, 87 mg/L, respectively. Copper, Na, hardness, Pb, nitrate+nitrite-nitrogen and total solids concentrations were 390 Fg/L, 2.4 mg/L, 350 mg/L, 12 Fg/L, <1.00 mg/L, 746 mg/L. Both Se and Ag were not detected. Arsenic and Cd concentrations were 720 Fg/L and 53 Fg/L, respectively. Arsenic and Cd exceeded the SDWA maximum contaminant levels (MCL). Iron, Mn, Zn, and sulfate concentrations were 80 mg/L, 490 Fg/L, 20000 Fg/L, and 330 mg/L, respectively). Iron, Mn, Zn, and sulfate concentrations also exceeded the SDWA secondary standards set by the EPA. Furthermore, these results indicated the need to analyze the packer test samples not only for As but for Cd, Fe, Mn, Zn and sulfate to further delineate the zones of poor water quality. Well 1 - Water Quality Packer Test The results of water samples collected from the packer test intervals at Well 1 (Figure 3) show a general decline in As concentrations with depth within the well column. The upper portion of the St. Peter Sandstone (34.7 m to 43.9 m) exhibits higher As concentrations than those found in the base of the St. Peter Sandstone (43.9 m to 62.2 m) and in the Cambrian sandstones (71.3 m to 91.4 m) found below it. While As concentrations within the borehole water increase in the Cambrian sandstones, they were below the SDWA and much below the concentration in the upper St. Peter Sandstone. Iron concentrations follow the same trend as As with higher concentrations in the upper St. Peter Sandstone. The Fe concentration in the well water declines in the lower portion of the St. Peter Sandstone and then rises somewhat within the Cambrian sandstones. The Fe concentration in the samples collected from the packer test remains above the SDWA welfare standard (0.3 mg/L) throughout the entire well column. However, the Fe concentrations are significantly reduced from that of the original well which had a Fe concentration of 80 mg/L. As a result of this packer test the potable well was deepened to 91.4 m by casing through the upper St. Peter Sandstone to 45.7 m. The resulting As concentration after reconstruction is 12 Fg/L, a substantial reduction from the original 1200 Fg/L As. Well 4 - Water Quality In addition to elevated As and Fe levels of 360 Fg/L and 250 mg/L respectively, Well 4 also had an unusually low field pH of 3.8. The water sample was analyzed for Ca, Cl, conductivity, alkalinity, hardness, Mg, Na, sulfate and total solids. Arsenic exceeded the SDWA maximum contaminant levels (MCL). Iron and sulfate also exceeded the SDWA secondary standards set by the EPA. A caliper log and gamma-ray log were run on Well 4 because the well had no subsurface information available below 36.6 m. Well 4 - Water Quality Packer Test The results from the Well 4 packer test indicated that the As concentrations throughout the entire well column remained above the SDWA MCL of 50 Fg/L. The As concentration was highest (>1,000 Fg/L) at the contact between the Prairie du Chien and the underlying Cambrian sandstones (83.2 m to 87.8 m) (Figure 4). However, this concentration likely resulted from the excessive colloidal sediment found in this zone. The bottom 6.1 m of the well was filled in with sediment. Even though the sample was filtered the WSLH noted abundant colloidal material which was acidified and analyzed with the sample. Elsewhere throughout the well column As concentrations were highest in the upper portions of the St. Peter Sandstone (610 Fg/L). Arsenic concentrations declined to 51 Fg/L at the bottom of the St. Peter Sandstone. The packer test results show the As concentration increasing in the Prairie du Chien dolomite (55.8 m to 75.6 m). Iron concentrations found in all packer test intervals exceeded the SDWA secondary standard for Fe of 0.3 mg/L. Iron concentrations exceeding the standard typically cause aesthetic nuisance problems such as odor and staining. In addition, Cd levels exceeded the SDWA MCL of 10 Fg/L in all of the packer intervals analyzed for Cd. Copper concentrations exceeded the SDWA MCL of 1300 Fg/L in only the lowest interval, which contained large amounts of sediment and colloidal material in the sample. Manganese concentrations remained over the EPA SDWA secondary standard of 50 Fg/L in all of the packer intervals analyzed. Zinc concentrations exceeded the SDWA secondary standard of 5000 Fg/L in all but one of the packer intervals tested. The possible presence of drilling grease, thread goop and galvanized pipe are insufficient to attribute these as the source for a problem of this magnitude and breadth. An unusually low field pH of 3.8 was recorded for Well 4, which provides an explanation as to why excessive amounts of metals were present in the water supply. As pH decreases, the metal ion concentrations in the groundwater tend to increase. Low pH values found in the well water may dissolve metallic minerals in the aquifer, increasing the metal ion concentrations. A replacement well has since been drilled on this property approximately 30.5 m away from the original well and is cased into the Prairie du Chien dolomite. The replacement well draws water from that dolomite and the underlying Cambrian sandstone and has tested to be below 2.2 Fg/L As which is a substantial reduction from the original 360 Fg/L As. The pH of this new well was not determined. Two wells in Outagamie County, Wells 2 and 3, were found also to have low pHs. Well 2, in Oneida Township, has a pH of 2.5 and well 3 in Greenville Township, had a pH of 3.0 . Similarly to Well 4, As, Fe, Cd and Pb ( 5,900, 740,000, 210, 160 Fg/L, respectively) were excessively elevated in well water obtained from Well 2. Also, through extensive investigation using geophysics, boring, and monitoring well installation, the WDNR has determined this pH is caused by pyrite oxidation (WDNR, 1994). A new well was drilled to replace Well 2. This replacement well draws water from the Platteville/Galena Dolomite, has an As value of 4 Fg/L compared to 5900 Fg/L and a pH of 8.22 compared to 2.5 . The original Well 3, which was located within 1.6 km of Well 4 in Greenville Township, had a recorded pH of 3.0 in 1967. Other nearby wells were sampled and did not exhibit similar low pH values at that time. A new well was drilled to provide potable water with a pH between 6.0 - 9.0. However a new well construction form was not completed by the driller and further analytical information is not available for the new well. The Well 4 packer test results showed that the pH in the well varied throughout the well column. The pH of the water from the upper portion of the St. Peter Sandstone was substantially lower pH than that of lower portions of the well. It is likely that the acid in the Well 4 water is derived from minerals within the St. Peter Sandstone that have oxidized to form sulfuric acid. Lithological analyses have identified arsenic-bearing pyrite and marcasite (FeS2) to occur within the Platteville/Galena Dolomite and St. Peter Sandstone. Many wells in the study area with elevated As concentrations may not exhibit low pH values due to the mixing and dilution within the entire well column. Only a few natural reactions are known to cause low pH in groundwater. Driscoll (1986) mentions that the acids from mine waters are produced from the oxidation of iron pyrite or other metal sulfide minerals to form sulfuric acid (H2SO4) . Oxidation of trace quantities of pyrite and marcasite does contribute to the acidic nature of groundwater (Bierens de Haan, 1991). Even the simple placement of a marble size field sample of this sulfide material in 250 ml of distilled water reduced the pH from 7.0 to 2.0 overnight. Oxidation of pyrite may also cause elevated levels of As in groundwater because As tends to be associated with pyrite and other sulfide minerals. The presence of marcasite and pyrite was documented in Well 2, in abundant quantities from a rock core through the upper St. Peter Sandstone (WDNR, 1994). Laboratory analysis of the sulfide rock material obtained from these Well 2 location cores showed As was present at 150 mg/kg. It is plausible that pyrite and marcasite may also be found in larger lenses or fractures of adjacent rock. Oxygen may be provided to the iron-rich water flowing from the aquifer at the well/rock interface at the borehole column, or by drilling and pumping (Smith and Tuovinen, 1985). Highly acidic environments in aquifers are rare. However, wells with pH values as low as 2.5 can occur as described in Wells 2, 3 and 4. New Well Construction and Well Reconstruction Packer tests showed a marked increase in As concentration in water from the upper portion of the St. Peter Sandstone. Water from the lower St. Peter Sandstone and the Prairie du Chien units had much lower As concentrations. To minimize As levels in groundwater supplies, the results suggest that one should avoid extracting well water from the upper portion of the St. Peter Sandstone aquifer (Figure 5) within the As advisory area (shown in Figure 1). Arsenic concentrations in private well water have been reduced to below the SDWA MCL by constructing new wells or reconstructing existing wells. A total of 17 wells have been reconstructed or constructed in a new location as part of this study. Two new wells were drilled shallower to draw water only from the Platteville/Galena Dolomite, thus removing the underlying St. Peter Sandstone as the source of water altogether. The other wells were deepened and the casing was extended below the upper St. Peter Sandstone preventing this zone from directly contributing water to the well. Some wells utilized water exclusively from the Prairie du Chien Dolomite. The other wells obtained water jointly from the Prairie du Chien Dolomite and the underlying Cambrian Sandstone. Fifteen of 17 reconstructions have successfully reduced As concentrations significantly below the SDWA MCL. CONCLUSIONS AND RECOMMENDATIONS This study of As levels in private wells in Brown, Marinette, Oconto, Outagamie, Shawano and Winnebago Counties has shown that a significant number of wells are affected by high As levels. The present SDWA MCL of 50 Fg/L As was exceeded on average of 4.0% of the total wells tested in Brown, Marinette, Oconto, Outagamie, Shawano and Winnebago Counties. This study has provided three lines of evidence that the As found in the groundwater in Outagamie, Winnebago and Brown Counties is of natural origin. First, the pattern of As contaminated wells is over 56.3 km long covering an area of approximately 951 km2. The aerial extent of the contamination alone clearly suggests that the source of As is not of an anthropogenic source. Also, historical storage of arsenic-based pesticides, such as sodium arsenite used in Wisconsin in the 1930's and 1940's for grasshopper control did not occur in these areas. Second, there are a number of natural sources that can contribute to arsenic in groundwater. Lithological analyses have identified the presence of pyrite and marcasite in the upper St. Peter Sandstone in Well 2 and 4, previously mentioned. Pyrite as the principal carrier of As in rocks, tends to be associated with mineral deposits of sulfides and sulfo-salts (Eisler, 1988). Pyrite exists in layers within the upper St. Peter Sandstone or lower Platteville/Galena Dolomite and thus can contribute As to groundwater. Third, groundwater extracted during packer tests show that the highest levels of As occur in the upper St. Peter Sandstone. As previously mentioned, pyrite layers occur within the upper St. Peters Sandstone and can contribute As to groundwater. Computer mapping, utilizing a Geographic Information System (GIS) proved to be a valuable tool to identify the approximate geographic regions in each county where private wells are affected by naturally occurring As. Nearly all sampled private wells which exceed the SDWA MCL for As are within a 8 km zone east or west of the mapped St. Peter Sandstone subcrop extending SW to NE through Outagamie and Winnebago Counties. Private wells exceeding the SDWA MCL in Brown County are shown to be localized in a specific area. No exceedances of the SDWA MCL for As was found in the wells sampled in Oconto, Marinette and Shawano Counties. The aerial distribution of wells within various As concentration ranges were used to develop an As advisory area in Outagamie and Winnebago Counties. Since most private wells within Outagamie and Winnebago Counties range between 30.5 m and 48.8 m deep, wells within the advisory area commonly draw water from the St. Peter Sandstone. Those private wells, located outside the 8.0 km boundary from the St. Peter Sandstone, that are drilled deeper than normal may encounter the formation and therefore may contain As, as has happened in Brown County 16 km downdip eastward. Recommendations were identified through this project for private well users to eliminate or greatly reduce their exposure to As in their drinking water supply. Also, guidelines were developed for well drillers in the area to eliminate and/or greatly reduce As exposure in water wells. The guidelines are as follows: If As concentration exceeds SDWA MCL: (1) purchase bottled water, (2) install a state approved water treatment device such as a distillation or reverse osmosis unit, to remove As (3) reconstruct the existing well, or drill a new well that avoids water from the upper St. Peters Sandstone formation If drilling a new well in the advisory area: (5) sample well water for As (6) construct the well to avoid water from the upper St. Peter Sandstone formation To avoid high As, the St. Peter Sandstone formation should not be penetrated, especially near the mapped subcrop. If it is necessary to drill through the St. Peter Sandstone to obtain a sufficient volume of water, t